Suppose a communications system is designed with K circuits so that if one is in use another can be chosen. Assume j circuits are in use and a circuit is chosen at random (without replacement) until a circuit not in use is selected.

(a) What is the chance that at least two selections are required?

(b) What is the chance that exactly two selections are required?

(c) What is the chance that exactly i selections are required, for i = 1, 2, . . .?